1. Field of the Invention
The present invention relates to a sheet supply apparatus of a so-called frictional separating method type. The sheet supply apparatus of such type can separate a sheet from sheets stacked therein by utilizing friction between a sheet supply roller and a separating plate.
2. Description of the Related Art
A sheet supply apparatus is such a machine that separates and feeds out stacked sheets one by one. Such sheet supply apparatus is usually installed in a printing machine, for example.
FIGS. 8 to 10 illustrate one example of such conventional sheet supply apparatus.
The sheet supply apparatus includes a sheet supply roller 1 and a separating base 2. The sheet supply roller 1, a separating member, is situated to a predetermined position and driven to rotate. The separating base 2, a separating member, is situated below the sheet supply roller 1.
The sheet supply roller 1 includes a core 3 and a roller member 4 integrally connected to an outer circumferential surface of the core 3. The core 3 is connected to a sheet supply shaft 5. The sheet supply shaft 5 is connected to a not-shown drive shaft.
The separating base 2 includes a high-friction member 6 and a curved stainless plate member 7 situated to a sheet-entrance side of the base. The sheet supply roller 1 contacts the high-friction member 6 of the separating base 2. Sheets fed thereto are separated from each other so that only one of the sheets can be conveyed forward.
A supporting plate 8 is fixed to a predetermined position. A lever 10 is pivotally movably attached to the supporting plate 8 by a support screw 9. The separating base 2 is attached to the lever 10 by a pin 11 so as to rotate around the pin. The separating base 2 can be detached from the pin 11. The supporting plate 8 has an attachment plate 12 integrally formed therewith. Through holes 8a and 12a are formed in a bottom of the supporting plate 8 and the attachment plate 12, respectively. A pressing pole 13 as a pressing member is inserted through the through holes 8a and 12a. The pressing pole 13 can move vertically along an axial direction of itself. A flange 14 is attached to the pressing pole 13 between the bottom of the supporting plate 8 and the attachment plate 12. An adjusting plate 15 as adjusting means is slidably situated on an upper surface of the bottom of the supporting plate 8. The adjusting plate 15 is longitudinal in a sliding direction of itself and narrow in a width direction. A slit 16 is formed in the adjusting plate 15 along the longitudinal direction thereof. The pressing pole 13 is inserted through the slit. An operating surface 17 is formed on both sides of the slit 16 on an upper surface of the adjusting plate 15. A height of the operating surface 17, i.e. a thickness of the adjusting plate 15, changes gradually along the longitudinal direction of the adjusting plate 15. One end portion of the adjusting plate 15 is designated as an operating end 18 and situated inside a casing of the present sheet supply apparatus. And, a spring 19 as urging means is disposed around the pressing pole 13 between the flange 14 and the adjusting plate 15.
In the constitution explained above, sheets are rubbed between the sheet supply roller 1 and the separating base 2, and conveyed forward by the sheet supply roller 1. When a plurality of the sheets reaches the separating base 2 while stacking with each other, the sheets are separated by the sheet supply roller 1 and the separating base 2 so that only one sheet can be conveyed forward. Here, the order FA. FC. FB is preferable where FA is a frictional force exerted between the sheet supply roller 1 and the printing sheet, FB is a frictional force exerted among the printing sheets, and FC is a frictional force exerted between the printing sheet and the separating base 2.
If difference among the frictional forces is not sufficient, the printing sheet may not be conveyed, or a plurality of the printing sheets is conveyed while not being separated from each other. The former phenomenon is called xe2x80x9cconveyance failurexe2x80x9d, and the latter xe2x80x9cmultiple conveyancexe2x80x9d.
The adjusting means explained above is used to properly arrange the difference among the frictional forces. The surface of the printing sheet is rough because it is composed of intertwined fibers. When the sheet supply roller 1 of a soft material is pressed against the printing sheet so that a nip width in which the printing sheet is held is enlarged, the frictional force between the sheet supply roller 1 and the printing sheet is enlarged and stabilized. If the nip width is small, the frictional force tends to decrease due to surface abrasion of the sheet supply roller 1 and paper powder generated from the printing sheets. Since many types of the printing sheets are in use, the frictional force among the sheets is varied accordingly. Therefore, stable conveyance of the printing sheet of many types inevitably requires the above-explained adjusting means for adjusting separating pressure. The separating pressure is to be adjusted by users so as to conform to a type of the sheet to be used.
In the constitution explained above, the pressing pole 13 is elastically urged upward by the spring 19 relative to the supporting plate 8. A top end of the pressing pole 13 presses up the lever 10. The separating base 2 attached to the lever 10 is urged upward to contact the sheet supply roller 1.
The separating pressure exerted on the sheet supply roller 1 by the separating base 2 can be adjusted by operating the adjusting plate 15. A user is to detach a part of a casing of the present apparatus to expose the operating end 18. The user is to take the operating end 18 and pull the adjusting plate 15 to slide along the longitudinal direction thereof. When the adjusting plate 15 thus slides, the height of the operating surface 17 of the adjusting plate 15 is changed at a position where the spring 19 is disposed. FIGS. 8 and 10 show that the spring 19 is supported by a relatively low operating surface 17, which means the separating pressure is small. FIG. 9 shows that the spring 19 is supported by a relatively high operating surface 17, which means the separating pressure is large.
After the adjustment is finished, the part is attached to the casing, and then the sheet supply apparatus is actually operated to feed the printing sheets, so that effect of adjusting the separating pressure is confirmed. If no effect is confirmed, the part of the casing is again detached and the adjustment is conducted once more.
In the conventional sheet supply apparatus as stated above, elastic force of the spring 19 is changed by sliding the adjusting plate 15. Accordingly, the adjusting plate 15 is required to be made in a longitudinal form along the sliding direction. Additionally, any other parts or members can not be allowed to be placed in a space where the adjusting plate 15 slides so as to prevent interference therewith. Thus, in the conventional sheet supply apparatus, an inside space thereof is not utilized effectively.
In the conventional sheet supply apparatus, the slidable adjusting plate 15 is downsized to its limit so as to utilize any of the inside space. Accordingly, the operating end 18 of the adjusting plate 15 must be placed inside the apparatus. This means that the operating end 18 cannot project out the apparatus. Therefore, when adjustment of the separating pressure is needed, the casing must be opened by detaching the part therefrom.
In the conventional sheet supply apparatus, since the longitudinal adjusting plate 15 slides along the longitudinal direction thereof, a groove 8b must be formed in the supporting plate 8 for guiding the adjusting plate 15 to slide therein. This groove 8b deteriorates strength of the supporting plate 8.
This invention is made to solve the problems as explained above. An object of the present invention is to provide a sheet supply apparatus which is enough compact to be situated in a small space and can be easily operated from the outside thereof.
According to a first aspect of the present invention, there is provided a sheet supply apparatus comprising a sheet supply member for supplying printing sheets; a separating member movably situated adjacent to the sheet supply member; a pressing member movably situated adjacent to the separating member; an urging device disposed near the pressing member for urging the pressing member toward the separating member so that the separating member contacts the sheet supply member;, and an adjusting device connected to the urging device for adjusting an urging force exerted on the pressing member by the urging device, the adjusting device including a rotationally operating portion and a rotationally adjusting portion connected to the rotationally operating portion, the rotationally adjusting portion being situated adjacent to the pressing member and the urging member and adjusting the urging force while being operated by the rotationally operating portion.
According to a second aspect of the present invention, there is provided a sheet supply apparatus comprising a sheet supply roller for supplying printing sheets; a separating member pivotally movably situated adjacent to the sheet supply roller; a pressing member movably situated adjacent to the separating member for pressing the separating member toward the sheet supply roller; an operating portion pivotally movably situated adjacent to the pressing member; an urging device situated between the pressing member and the operating portion, the urging device urging the pressing member toward the separating member; rotationally adjusting portion cooperating with the operating portion, the rotationally adjusting portion moving the operating portion while being rotated so that an urging force exerted on the separating member by the urging device through the pressing member is adjusted; and a rotationally operating portion connected to the rotationally adjusting portion for rotating the rotationally adjusting portion.
According to a third aspect of the present invention, there is provided a sheet supply apparatus comprising a sheet supply roller for supplying printing sheets; a separating member pivotally movably situated adjacent to the sheet supply roller; a pressing member movably situated adjacent to the separating member for pressing the separating member toward the sheet supply roller; a cam rotatably situated adjacent to the pressing member; an urging device situated between the pressing member and the cam, the urging device urging the pressing member toward the separating member; and a rotationally operating portion connected to the cam for rotating the cam so that an urging force exerted on the separating member by the urging device through the pressing member is adjusted.
A sheet supply apparatus as defined in a fourth aspect of the present invention, in the second aspect of the present invention, further comprises a case containing the sheet supply roller and the separating member therein, and the rotationally operating portion is operated from an outside of the case.
A sheet supply apparatus as defined in a fifth aspect of the present invention, in the second aspect of the present invention, further comprises a fixing device situated at the rotationally operating portion, and the fixing means fixes the rotationally operating portion to an optional position in a rotational direction thereof.
A sheet supply apparatus as defined in a sixth aspect of the present invention, in the third aspect of the present invention, further comprises a case containing the sheet supply roller and the separating member therein, and the rotationally operating portion is operated from an outside of the case.
A sheet supply apparatus as defined in a seventh aspect of the present invention, in the third aspect of the present invention, further comprises a fixing device situated at the rotationally operating portion, and the fixing device fixes the rotationally operating portion to an optional position in a rotational direction thereof.